Heat butter over medium heat in a medium saucepan. Add garlic and cook 1 minute. Whisk in flour. Continue to whisk and let cook 1 minute.

Slowly stir in milk. Allow to cook 3-4 minutes, just until thickening, stirring occasionally. Remove mixture from heat and stir in cheese. Stir until smooth and then stir in the sriracha sauce.

Serve immediately, or pour into a small slow cooker, set to warm to keep warm until serving.

Garnish with chopped scallions and additional drops of sriracha, if desired.